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A solid agricultural waste, coffee husk, was applied as an adsorbent for reactive dye-polluted wastewater treatment. Coffee husk biochar was pyrolyzed at 450 °C and then chemically activated using 50% ZnCl2 solution. The surface of activated coffee husk biochar was modified using a cationic surfactant, Cetyltrimethylammonium bromide (CTAB), to create CTAB-modified coffee husk biochar (MCH), to improve reactive adsorption of anionic dyes from synthetic wastewater. The selected reactive dyes were reactive yellow 145 (RDY145), reactive red 195 (RDR195), and reactive blue 222 (RDB222). The adsorption kinetics fit well using a pseudo-second order model for all three dyes. The adsorption isotherms matched well with the Langmuir model .The removal efficiency of RDY145 (83.7%) was the highest, followed by RDR195 (71.1%) and RDB222 (59.6%). The amount of RDY145 adsorbed by MCH was about 9-fold that adsorbed by conventional activated carbon. Additionally, the solution pH had no effect on reactive dye removal efficiency using MCH.

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Nonionic surfactants have been utilized to improve the enzymatic hydrolysis of lignocellulosic materials. However, the role of surfactant adsorption affecting enzymatic hydrolysis has not been elaborated well. In this work, nonionic surfactants differing in their molecular structures, namely the polyoxyethylene sorbitan monooleate (Tween 80), the secondary alcohol ethoxylate (Tergitol 15-S-9), and the branched alcohol ethoxylate (Tergitol TMN-6), were studied for their effects on the enzymatic hydrolysis of palm fruit bunch (PFB). The PFB was pretreated with a 10% w/v sodium hydroxide solution and then hydrolyzed using the cellulase enzyme from Trichoderma reesei (ATCC 26921) at 50 °C and pH 5. The optimal conditions providing similar yields of reducing sugar required Tween 80 and Tergitol TMN-6 at 0.25% w/v, while Tergitol 15-S-9 was required at 0.1% w/v. All the surfactants improved the enzymatic conversion efficiency and reduced unproductive binding of the enzyme to lignin. In addition, the adsorption isotherm of cellulase was fit well by the Freundlich isotherm, while adsorption of the three nonionic surfactants agreed well with the Langmuir isotherm. Adsorption capacities of the three nonionic surfactants were consistent with their enhancement efficiencies in hydrolysis. The critical micelle concentration was observed as a key property of nonionic surfactant for adsorption capacity.

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Cloud point extraction (CPE) has shown to be an effective technique to remove organic compounds from contaminated water using nonionic surfactant as a separating agent. To make this process more economically attractive, the spent nonionic surfactants should be recycled and reused. This work utilized a packed column operated under vacuum in co-current mode to remove the volatile organic compounds (VOCs) from the secondary alcohol ethoxylates, AEs, coacervate solution. The co-current operation can effectively avoid plugging, excessive foaming, and flooding. The selected volatile organic contaminants are aromatic hydrocarbons such as benzene, toluene, and ethylbenzene. The hydrophobic properties of the VOCs are described by an octanol-water partition coefficient (Kow). The results show that as the Kow increases, the Ks substantially increases while the Happ of the VOCs significantly decreases. The reduction of VOCs volatilization is possibly due to greater partitioning of the VOCs into surfactant micelles. The similar trend is also observed in the continuous operation. The results show that as the Kow increases, the percentage of VOCs removal and the Kxa decrease due to the VOCs’ hydrophobic effect. The removal percentages of the VOCs vary from 60 to 90%. The R2 of the log-log and semi-log relationships between Kow and studied parameters are observed in the range of 0.96-0.99.

The interest in using benign surfactants has been steadily increasing in the context of enhanced oil recovery (EOR). Palm kernel alkanolamide surfactant (PKA), a nonionic surfactant synthesized from palm kernel oil, was preliminarily assessed for EOR from sandstone reservoir rocks. The performance factors determined were surfactant loss due to adsorption on silica surface and crude oil solubilization for oil solubilizing efficiency. The performance of PKA was compared to two commercial ionic surfactants, SDS (anionic surfactant) and CTAB (cationic surfactant). The results show that PKA was less absorbed on silica than CTAB or SDS. The adsorption kinetics was well fit with a pseudo-second order model for all three surfactants. The adsorption equilibrium data for CTAB and PKA were fitted with a Langmuir isotherm, while a Freundlich isotherm fit well for SDS, indicating multilayer SDS adsorption on silica surfaces. The adsorption of PKA was not significantly affected by added NaCl or increased temperature. In addition, the solubilization equilibrium constant (Ks) had the rank order PKA>CTAB>SDS, and proportionally increased with added NaCl. PKA performance was also compared to two commercial nonionic surfactants, Tergitol 15-S-9 and Tergitol TMN-6, and the results indicate that PKA was the least adsorbed, and had the highest Ks among the tested nonionic surfactants.